The overall objectives are to discover how to attach substitution-inert metal centers to specific sites on molecules of biochemical interest, and to study the changes in reactivity and in other properties, which attend the coordination. When the complex in which the amino function of ethylglycinate is coordinated to the pentaammineruthenium (III) moiety is acidified, a remarkable linkage isomerization occurs, producing the carboxylate complex of pentaammineruthenium (III) and ethanol. This kind of activation apparently takes place also in ethylglycylglycinate, leading to peptide bond hydrolysis. The reaction seems to have the potential of being developed into a facile method of end-specific peptide hydrolysis; it will be explored with a variety of amino acid esters and peptides, and an effort will be made to enhance the effect by changing the auxiliary ligands on ruthenium (III). Rutheniumpentaammineruthenium (III) makes a substitution-inert bond to thio ethers. Reactivities which result from the electron withdrawing effect of the metal centers will be explored, particularly with methionine as the sulfur containing ligand. Nitrido complexes of osmium (VI) are labile to substitution in the position trans to the nitrido ligand. On reduction to osmium (III), the system becomes fully inert to substitution; specificities for attachment which may result from this strategy among polar groups such as amines, imidazole and carboxylates will be explored.